1. Field of the Invention
The present invention relates to an inkjet recording apparatus for performing recording on a recording medium by discharging ink and a control method of the inkjet recording apparatus.
2. Description of the Related Art
An inkjet recording method is a method for performing recording by discharging liquid (for example, ink) from discharge ports of an inkjet recording head so that the liquid adheres onto a recording medium such as paper. The inkjet recording method can perform high image quality and high-speed recording by using bubbles of the liquid caused by thermal energy produced in a heating unit and discharging the liquid.
Generally, the inkjet recording head includes a plurality of inkjet discharge ports, an ink flow path communicating with the ink discharge ports, and a heating unit producing thermal energy for discharging the ink. To the ink flow path, the ink is supplied from an ink tank, and the supplied ink is reserved in the vicinity of the ink discharge ports. In such a state, if the heating unit is driven and thermal energy is produced, the ink in the vicinity of the ink discharge ports is heated by the thermal energy and bubbles are formed. By pressure caused by the bubbling, the ink is discharged.
In such a mechanism, an ink contact portion (heat affected portion) of the heating unit that is heated by the heating unit is subjected to a multiple effect including cavitation impact due to bubbling or contraction of the ink and chemical functioning by the ink while being exposed to high temperatures when the ink is discharged. Generally, in order to reduce the cavitation impact or the influence of the chemical functioning due to the ink, a protective layer including a metallic material is provided to the heat affected portion. The temperature of the surface of the protective layer may increase to around 700° C., and the surface comes in contact with the ink. Accordingly, for the material used for the protective layer, it is required to have excellent heat resistance, mechanical characteristics, chemical stability, alkaline resistance, and the like.
At the same time, if color materials, added substances, and the like contained in the ink are decomposed by high temperature heating, the materials may change into low solubility materials (hereinafter, such materials are also referred to as a burnt deposit). If the materials adhere to the heat affected portion of the protective layer, the heat is not uniformly conducted from the heating unit to the ink, and results in unstable bubbling. Then, the ink may not be discharged. To solve this issue, in the inkjet recording apparatuses, the burnt deposit needs to be removed from the heat affected portion of the inkjet recording head at appropriate timing.
Japanese Patent Application Laid-Open No. 2008-105364 discusses an inkjet recording apparatus in which cleaning of an inkjet recording head is performed when the number of times of ink discharge exceeds a predetermined value in order to remove the burnt deposit.
However, an adhesion state of the burnt deposit onto the heating unit of the inkjet recording head varies depending on the type of the ink or the recording method. Accordingly, it is necessary to correctly determine whether the burnt deposit adheres to the heat affected portion.